1. Field of the Invention
The present invention relates generally to implantable prostheses and in particular to prostheses including a selectively applied bone growth promoting agent.
2. Description of Related Art
Currently, only implantable hip and knee prostheses include some type of provision that promotes bone growth. In the past, various types of treatments or modifications to the surface of these prosthesis have been included that promote bone growth.
Screws with porous surfaces have been proposed. Serbousek (U.S. Pat. No. 5,098,434) teaches a screw for mounting a prosthetic component onto an underlying bone. The screw includes a head and an elongated cylindrical shank that is integral with and extends from the head. The shank includes a threaded member and a shoulder member having an outer surface with a porous medium for encouraging bone ingrowth fixation. The Serbousek screw is utilized in securing a hip prosthesis (acetabular cup) to the pelvis.
These screws are involved in securing the implants into one boney surface, for example, femeral stem component to the femur, an acetabular cup to the pelvis, distal femeral knee prosthesis to the femur or a tibial component to the tibia.
Tharmann (U.S. Pat. No. 5,360,448) teaches another porous-coated bone screw for securing a joint prosthesis. In the design of Tharmann, bone screws are proposed with and without heads. The bone screws include a shaft provided with axially adjacent longitudinally extending portions. These extending portions include bone ingrowth porous surfaces and alternate with portions having threaded surfaces.
While the related art teaches various forms of hip and knee prostheses with provisions for promoting bone growth, there are no provisions made for these surfaces and coatings being applied to trauma implants, fracture devices and implants, and fusion implants including rods, screws, plates and fusion cages. Related art prostheses lack selectively applied bone growth promoting treatments, and bone growth promoting treatments are not applied to general orthopedic implants. Generally, the bone growth treatments are applied along the prosthesis used in joint replacements and have been described only inside cylindrical threaded fusion cages. In these fusion cages, the bone promoting agent (BMP, OP1) is placed within the cage and its purpose is to allow for bony growth through the cage from one vertebra to another, in order to create a fusion. These bone growth treatments are not applied to the surface of the implants, and therefore do not induce the incorporation of the bone to the implant itself. The prior art does not teach the selective application of the variety of known bone growth promoting treatments for use in general orthopedic implants.
Additionally, the prostheses disclosed in the prior art do not include through-holes that permit bony integration into the implant. This refers to the fact that hip and knee prostheses are flat surfaces without holes. Also, pattern specificity is not disclosed in the prior art. Currently, hip and knee prosthesis only includes a partial coating to the proximal portion to the hip prosthesis but this technique is not used in general orthopedic implants.
Additionally, the prostheses disclosed in the prior art do not include through-holes that permit bone integration. Also, pattern specificity is not disclosed in the prior art. There is therefore a need in the art for prostheses that incorporate selectively applied bone growth promoting treatments.